regext J. Latour
Internet-Draft CIRA
Intended status: Standards Track O. Gudmundsson
Expires: September 13, 2017 Cloudflare, Inc.
P. Wouters
Red Hat
M. Pounsett
Rightside Group, Ltd.
March 12, 2017

Third Party DNS operator to Registrars/Registries Protocol


There are several problems that arise in the standard Registrant/Registrar/Registry model when the operator of a zone is neither the Registrant nor the Registrar for the delegation. Historically the issues have been minor, and limited to difficulty guiding the Registrant through the initial changes to the NS records for the delegation. As this is usually a one time activity when the operator first takes charge of the zone it has not been treated as a serious issue.

When the domain uses DNSSEC it necessary to make regular (sometimes annual) changes to the delegation, updating DS record(s) in order to track KSK rollover. Under the current model this is prone to delays and errors, as the Registrant must participate in updates to DS records.

This document describes a simple protocol that allows a third party DNS operator to update DS records for a delegation, in a trusted manner, without involving the Registrant for each operation. This same protocol can be used by Registrants.

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at

Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."

This Internet-Draft will expire on September 13, 2017.

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Table of Contents

1. Introduction

After a domain has been registered, one of three parties will maintain the DNS zone loaded on the "primary" DNS servers: the Registrant, the Registrar, or a third party DNS operator. DNS registration systems were originally designed around making registrations easy and fast, however after registration the complexity of making changes to the delegation differs for each of these parties. The Registrar can make changes directly in the Registry systems through some API (typically EPP [RFC5730]). The Registrant is typically limited to using a web interface supplied by the Registrar. A third party DNS Operator must to go through the Registrant to update any delegation information.

In this last case, the operator must contact and engage the Registrant in updating NS and DS records for the delegation. New information must be communicated to the Registrant, who must submit that information to the Registrar. Typically this involves cutting and pasting between email and a web interface, which is error prone. Furthermore, involving Registrants in this way does not scale for even moderately sized DNS operators. Tracking thousands (or millions) of changes sent to customers, and following up if those changes are not submitted to the Registrar, or are submitted with errors, is itself expensive and error prone.

The current system does not work well, as there are many types of failures that have been reported at all levels in the registration model. The failures result in either the inability to use DNSSEC or in validation failures that cause the domain to become unavailable to users behind validating resolvers.

The goal of this document is to create a protocol for establishing a secure chain of trust that involves parties not in the traditional Registrant/Registrar/Registry (RRR) model, and to reduce the friction in maintaining DNSSEC secured delegations in these cases. It describes a REST-based [RFC6690] protocol which can be used to establish DNSSEC initial trust (to enable or bootstrap DNSSEC), and to trigger maintenance of DS records.

2. Notional Conventions

2.1. Definitions

For the purposes of this draft, a third-party DNS Operator is any DNS Operator responsible for a zone, where the operator is neither the Registrant nor the Registrar of record for the delegation.

Uses of "child" and "parent" refer to the relationship between DNS zone operators. In this document, unless otherwise noted, the child is the third-party DNS operator and the parent is the Registry.

Uses of the words "Registrar" or "Registration Entity" in this document may also be applied to Resellers or to Registries that engage in registration activities directly with Registrants. Unless otherwise noted, they are used to refer to the entity which has a direct business relationship with the Registrant.

2.2. RFC2119 Keywords

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].

3. Process Overview

3.1. Identifying the Registrar

As of publication of this document, there has never been a standardized or widely deployed method for easily and scalably identifying the Registar for a particular registration.

At this time, WHOIS [RFC3912] is the only widely deployed protocol to carry such information, but WHOIS responses are unstructured text, and each implementor can lay out its text responses differently. In addition, Registries may include referrals in this unstructured text to the WHOIS interfaces of their Registrars, and those Registrar WHOIS interface in turn have their own layouts. This presents a text parsing problem which is infeasible to solve.

RDAP, the successor to WHOIS, described in [RFC7480], solves the problems of unstructured responses, and a consistently implemented referral system, however at this time RDAP has yet to be deployed at most Registries.

With no current mechanism in place to scalably discover the Registar for a particular registration, the problem of automatic discovery of the base URL of the API is considered out of scope of this document. The authors recommend standardization of an RDAP extension to obtain this information from the Registry.

3.2. Establishing a Chain of Trust

After signing the zone, the child operator needs to upload the DS record(s) to the parent. The child can signal its desire to have DNSSEC validation enabled by publishing one of the special DNS records CDS and/or CDNSKEY as defined in [RFC7344] and [RFC8078].

In the case of an insecure delegation, the Registrar will normally not be scanning the child zone for CDS/CDNSKEY records. The child operator can use this protocol to notify the Registrar to begin such a scan.

Once the Registrar sees these records it SHOULD start acceptance processing.

3.3. Maintaining the Chain of Trust

One the secure chain of trust is established, the Registrar SHOULD regularly check the child zone for CDS/CDNSKEY record changes. The Registrar SHOULD also accept signals via this protocol to immediately check the child zone for CDS/CDNSKEY records.

Server implementations of this protocol MAY include rate limiting to protect their systems and the systems of child operators from abuse.

Each parent operator and Registrar is responsible for developing, implementing, and communicating their DNSSEC maintenance policies.

3.4. Other Delegation Maintenance

3.5. Acceptance Processing

The Registrar, upon receiving a signal or detecting through polling that the child desires to have its delegation updated, SHOULD run a series of tests to ensure that updating the parent zone will not create or exacerbate any problems with the child zone. The basic tests SHOULD include:

The Registrar SHOULD NOT make any changes to the DS RRset if the child name servers do not agree on the CDS/CDNSKEY content.

Registrars MAY require compliance with additional tests, particularly in the case of establishing a new chain of trust, such as:

4. API Definition

This protocol is partially synchronous, meaning the server can elect to hold connections open until operations have completed, or it can return a status code indicating that it has received a request, and close the connection. It is up to the child to monitor the parent for completion of the operation, and issue possible follow-up calls to the Registrar.

Clients may be denied access to change the DS records for domains that are Registry Locked (HTTP Status code 401). Registry Lock is a mechanism provided by certain Registries or Registrars that prevents domain hijacking by ensuring no attributes of the domain are changeable, and no transfer or deletion transactions can be processed against the domain name without manual intervention.

4.1. Authentication

The API does not impose any unique server authentication requirements. The server authentication provided by TLS fully addresses the needs of this protocol. The API MUST be provided over TLS-protected transport (e.g., HTTPS) or VPN.

Client authentication is considered out of scope of this document. The publication of CDS/CDNSKEY records in the child zone is an indication that the child operator intends to perform DS-record-updating activities (add/delete) in the parent zone. Since this protocol is simply a signal to the Registrar that they should examine the child zone for such intentions, additional authentication of the client making the request is considered unnecessary.

Registrars MAY implement their own policy to protect access to the API, such as with IP whitelisting, client TLS certificates, etc.. Registrars SHOULD take steps to ensure that a lack of additional authentication does not open up a denial of service mechanism against the systems of the Registrar, the Registry, or the child operator.

4.2. RESTful Resources

In the following text, "{domain}" is the child zone to be operated on.

4.2.1. CDS resource

Path: /domains/{domain}/cds Establishing Initial Trust (Enabling DNSSEC) Request

Syntax: POST /domains/{domain}/cds

Request that an initial set of DS records based on the CDS record in the child zone be inserted into the Registry and the parent zone upon the successful completion of the request. If there are multiple CDS records in the CDS RRset, multiple DS records will be added.

The body of the POST SHOULD be empty, however server implementations SHOULD NOT reject nonempty requests. Response

This request is for setting up initial trust in the delegation. The Registrar SHOULD return a status code 409 if it already has a DS RRset for the child zone.

Upon receipt of a 403 response the child operator SHOULD issue a POST for the "token" resource to fetch a challenge token to insert into the zone. Removing DS Records Request

Syntax: DELETE /domains/{domain}/cds

Request that the Registrar check for a null CDS or CDNSKEY record in the child zone, indicating a request that the entire DS RRset be removed. This will make the delegation insecure. Response Modifying DS Records Request

Syntax: PUT /domains/{domain}/cds

Request that the Registrar modify the DS RRset based on the CDS/CDNSKEY available in the child zone. As a result of this request the Registrar SHOULD add or delete DS records as indicated by the CDS/CDNSKEY RRset, but MUST NOT delete the entire DS RRset. Response

4.2.2. Token resource

Path: /domains/{domain}/token Establish Initial Trust with Challenge Request

Syntax: GET /domains/{domain}/token

The DNSSEC policy of the Registrar may require proof that the DNS Operator is in control of the domain. The token API call returns a random token to be included as a TXT record for the _delegate.@ domain name (where @ is the apex of the child zone) prior establishing the DNSSEC initial trust. This is an additional trust control mechanism to establish the initial chain of trust.

Once the child operator has received a token, it SHOULD be inserted in the zone and the operator SHOULD proceed with a POST of the cds resource.

The Registrar MAY expire the token after a reasonable period. The Registrar SHOULD document an explanation of whether and when tokens are expired in their DNSSEC policy.

Note that the _delegate TXT record is publicly available and not a secret token. Response

4.3. Customized Error Messages

Registrars MAY provide a customized error message in the response body in addition to the HTTP status code defined in the previous section. This response MAY include an identifying number/string that can be used to track the request.

5. Security considerations

When zones are properly provisioned, and delegations follow standards and best practices (e.g. [I-D.wallstrom-dnsop-dns-delegation-requirements]), the Registrar or Registry can trust the DNS information it receives from multiple child name servers, over time, and/or over TCP to establish the initial chain of trust.

In addition, the Registrar or Registry can require the DNS Operator to prove they control the zone by requiring the child operator to navigate additional hurdles, such as adding a challenge token to the zone.

This protocol should increase the adoption of DNSSEC, enabling more zones to become validated thus overall the security gain outweighs the possible drawbacks.

Registrants and DNS Operators always have the option to establish the chain of trust in band via the standard Registrant/Registrar/Registry model.

6. IANA Actions

This document has no actions for IANA

7. Internationalization Considerations

This protocol is designed for machine to machine communications. Clients and servers should use punycode [RFC3492] when operating on internationalized domain names.

8. References

8.1. Normative References

[RFC3492] Costello, A., "Punycode: A Bootstring encoding of Unicode for Internationalized Domain Names in Applications (IDNA)", RFC 3492, DOI 10.17487/RFC3492, March 2003.
[RFC6690] Shelby, Z., "Constrained RESTful Environments (CoRE) Link Format", RFC 6690, DOI 10.17487/RFC6690, August 2012.
[RFC7344] Kumari, W., Gudmundsson, O. and G. Barwood, "Automating DNSSEC Delegation Trust Maintenance", RFC 7344, DOI 10.17487/RFC7344, September 2014.
[RFC8078] Gudmundsson, O. and P. Wouters, "Managing DS Records from the Parent via CDS/CDNSKEY", RFC 8078, DOI 10.17487/RFC8078, March 2017.

8.2. Informative References

[I-D.wallstrom-dnsop-dns-delegation-requirements] Wallstrom, P. and J. Schlyter, "DNS Delegation Requirements", Internet-Draft draft-wallstrom-dnsop-dns-delegation-requirements-03, October 2016.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997.
[RFC3912] Daigle, L., "WHOIS Protocol Specification", RFC 3912, DOI 10.17487/RFC3912, September 2004.
[RFC5730] Hollenbeck, S., "Extensible Provisioning Protocol (EPP)", STD 69, RFC 5730, DOI 10.17487/RFC5730, August 2009.
[RFC6841] Ljunggren, F., Eklund Lowinder, AM. and T. Okubo, "A Framework for DNSSEC Policies and DNSSEC Practice Statements", RFC 6841, DOI 10.17487/RFC6841, January 2013.
[RFC7480] Newton, A., Ellacott, B. and N. Kong, "HTTP Usage in the Registration Data Access Protocol (RDAP)", RFC 7480, DOI 10.17487/RFC7480, March 2015.

Appendix A. Document History

A.1. regext Version 03

A.2. regext Version 02

A.3. regext Version 01

A.4. regext Version 00

A.5. Version 03

A.6. Version 02

A.7. Version 01

A.8. Version 00

Authors' Addresses

Jacques Latour CIRA Ottawa, ON EMail:
Olafur Gudmundsson Cloudflare, Inc. San Francisco, CA EMail:
Paul Wouters Red Hat Toronto, ON EMail:
Matthew Pounsett Rightside Group, Ltd. Toronto, ON EMail: